I agree with watching the Paperclipping videos where Noel talks about Project Life, but I also find myself using her flexible templates in Project Life all the time - so make sure those videos are at the top of your list too.
When I first started scrapbooking, I only did Project Life and I way over-embellished. It's a little scary looking back on those layouts from only 2 years ago and seeing how much stuff I put in those pockets. So, I've been there, and I know how you might be feeling!
My first bit of advice would be to look at the color of your photographs and use that to help you decide what colors to use in your layout. In this layout, I knew I would be using photographs of a bright yellow soup I had made and my boyfriend's office kitchen which is a bright green/yellow. So I decided to use cards with bright yellowish accents and then white and black/grey cards as to not compete visually with the bright pops of color. Secondly, keep it simple and don't put an embellishment on every card or on every photo. Leave some filler cards, where you might have only one embellishment or image or a few words (like I did with the heart card with the number 2 and the yellow card with the heart). When it came to assembling the page, I tried to place the bright accents in a visual triangle (something Noel talks lots about in her videos - loooove the visual triangle, use it ALL the time) across the two pages. I also always layout my pages side by side and think of it as one whole rather than two parts.
I am by no means a design expert, but that's just some of what I've learned as I've tried to embellish less/more smartly and have more cohesive Project Life layouts.